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A novel imprecise stochastic process model for time-variant or dynamic uncertainty quantification

Chinese Journal of Aeronautics 2022年第9期35卷 255-267页

作者： Jinwu LI Chao JIANG State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China

This paper proposes a novel model named as “imprecise stochastic process model” to handle the dynamic uncertainty with insufficient sample information in real-world problems. In the imprecise stochastic process model, the imprecise probabilistic model rather than a precise probability distribution function is employed to characterize the uncertainty at each time point for a time-variant parameter, which provides an effective tool for problems with limited experimental samples. The linear correlation between variables at different time points for imprecise stochastic processes is described by defining the auto-correlation coefficient function and the crosscorrelation coefficient function. For the convenience of analysis, this paper gives the definition of the P-box-based imprecise stochastic process and categorizes it into two classes: parameterized and non-parameterized P-box-based imprecise stochastic processes. Besides, a time-variant reliability analysis approach is developed based on the P-box-based imprecise stochastic process model,through which the interval of dynamic reliability for a structure under uncertain dynamic excitations or time-variant factors can be obtained. Finally, the effectiveness of the proposed method is verified by investigating three numerical examples.

关键词： Dynamic reliability analysis Epistemic uncertainty Imprecise random variable Imprecise stochastic process P-box model Time-variant uncertainty

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A reconstructed edge-based smoothed DSG element based on global coordinates for analysis of Reissner–Mindlin plates

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Acta Mechanica Sinica 2017年第1期33卷 83-105页

作者： Gang Yang De’an Hu Shuyao Long State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle Engineering Hunan University Changsha 410082China

A reconstructed edge-based smoothed triangular element, which is incorporated with the discrete shear gap (DSG) method, is formulated based on the global coordinate for analysis of Reissner-Mindlin plates. A symbolic integration combined with the smoothing technique is implemented to calculate the smoothed finite element matrices, which is integrated along the boundaries of each smoothing cell. Numerical results show that the proposed element is free from shear locking, and its results are in good agreement with the exact solutions, even for very thin plates with extremely distorted elements. The proposed element gives more accurate results than the original DSG element without smoothing, and it can be taken as an alternative element for analysis of Reissner-Mindlin plates. The prominent feature of the present element is that the integration scheme is unified in the smoothed form for all of the finite element matrices.

关键词： Reissner-Mindlin plate DSG method Symbolic integration Smoothing technique Global coordinate Distorted element

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Analysis and Optimization of the Electrohydraulic Forming Process of Sinusoidal Corrugation Tubes

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Fluid Dynamics & Materials Processing 2024年第4期20卷 873-887页

作者： Da Cai Yinlong Song Hao Jiang Guangyao Li Junjia Cui State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle Hunan UniversityChangsha410082China

Aluminum alloy thin-walled structures are widely used in the automotive industry due to their advantages related to light weight and *** can be produced at room temperature by the electrohydraulic forming *** the present study,the influence of the related parameters on the forming quality of a 6063 aluminum alloy sinusoidal corrugation tube has been *** particular,the orthogonal experimental design(OED)and central composite design(CCD)methods have been *** the range analysis and variance analysis of the experimental data,the influence degree of wire diameter(WD)and discharge energy(DE)on the forming quality was *** regression analysis was performed using the response surface methodology.A prediction model for the attaching-die state coefficient was established *** following optimal arrangement of parameters was obtained(WD=0.759 mm,DE=2.926 kJ).The attaching-die state coefficient reached the peak value of *** optimized wire diameter and discharge energy for a better attaching-die state could be screened by CCD compared with *** response surface method in CCD was more suitable for the design and optimization of the considered process parameters.

关键词： Electrohydraulic forming aluminum alloy tube process parameters attaching-die state 1 Introduction

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A meshfree-based local Galerkin method with condensation of degree of freedom for elastic dynamic analysis

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Acta Mechanica Sinica 2014年第1期30卷 92-99页

作者： De-An Hu Yi-Gang Wang Yang-Yang Li Xu Han Yuan-Tong Gu State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University School of Chemistry Physics and Mechanical EngineeringQueensland University of Technology

Condensation technique of degree of freedom is first proposed to improve the computational efficiency of meshfree method with Galerkin weak form for elastic dy- namic analysis. In the present method, scattered nodes with- out connectivity are divided into several subsets by cells with arbitrary shape. Local discrete equation is established over each cell by using moving Kriging interpolation, in which the nodes that located in the cell are used for approxima- tion. Then local discrete equations can be simplified by con- densation of degree of freedom, which transfers equations of inner nodes to equations of boundary nodes based on cells. The global dynamic system equations are obtained by as- sembling all local discrete equations and are solved by using the standard implicit Newmark＇s time integration scheme. In the scheme of present method, the calculation of each cell is carried out by meshfree method, and local search is imple- mented in interpolation. Numerical examples show that the present method has high computational efficiency and good accuracy in solving elastic dynamic problems.

关键词： Meshfree method Local Galerkin method Moving Kriging interpolation - Condensation of degree of freedom Computational efficiency

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Simultaneous Multi-vehicle Detection and Tracking Framework with Pavement Constraints Based on Machine Learning and Particle Filter Algorithm

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Chinese Journal of Mechanical Engineering 2014年第6期27卷 1169-1177页

作者： WANG Ke HUANG Zhi ZHONG Zhihua State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University College of Automotive Engineering Chongqing University

Due to the large variations of environment with ever-changing background and vehicles with different shapes, colors and appearances, to implement a real-time on-board vehicle recognition system with high adaptability, efficiency and robustness in complicated environments, remains challenging. This paper introduces a simultaneous detection and tracking framework for robust on-board vehicle recognition based on monocular vision technology. The framework utilizes a novel layered machine learning and particle filter to build a multi-vehicle detection and tracking system. In the vehicle detection stage, a layered machine learning method is presented, which combines coarse-search and fine-search to obtain the target using the AdaBoost-based training algorithm. The pavement segmentation method based on characteristic similarity is proposed to estimate the most likely pavement area. Efficiency and accuracy are enhanced by restricting vehicle detection within the downsized area of pavement. In vehicle tracking stage, a multi-objective tracking algorithm based on target state management and particle filter is proposed. The proposed system is evaluated by roadway video captured in a variety of traffics, illumination, and weather conditions. The evaluating results show that, under conditions of proper illumination and clear vehicle appearance, the proposed system achieves 91.2% detection rate and 2.6% false detection rate. Experiments compared to typical algorithms show that, the presented algorithm reduces the false detection rate nearly by half at the cost of decreasing 2.7%–8.6% detection rate. This paper proposes a multi-vehicle detection and tracking system, which is promising for implementation in an on-board vehicle recognition system with high precision, strong robustness and low computational cost.

关键词： simultaneous detection and tracking pavement segmentation layered machine learning particle filter

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Prediction and optimization of aerodynamic noise in an automotive air conditioning centrifugal fan

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Journal of Central South University 2013年第5期20卷 1245-1253页

作者：杨振东谷正气汪怡平颜建容杨晓涛 State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(Hunan University) School of Automobile Engineering Wuhan University of Technology

The high aerodynamic noise induced by automotive air conditioning systems has important effects on the ride comfort, and the centrifugal fan is the largest noise source in these systems. It is very important to reduce the aerodynamic noise generated by the centrifugal fan. The flow field and the sound field on the whole centrifugal fan configuration have been carried out using the computational fluid dynamics. Simulation results show that the sound pressure level near the outlet of the centrifugal fan is too high. Based on the relationship between flow characteristics and the aerodynamic noise, four parameters of the centrifugal fan, i.e., impeller blade＇s outlet angle 0, volute tongue＇s gap t, collector inclination angle fl, and rotating speed n, were selected as design variables and optimized using response surface methodology. While keeping the function of flow rate unchanged, the peak noise level is reduced by 8 dB or 10.8%. The noise level is satisfactorily reduced.

关键词： aerodynamic noise multi-forward-curved-blade centrifugal fan optimization response surface methodology

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Parameter Effects of the Potential‑Field‑Driven Model Predictive Controller for Shared Control

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Automotive Innovation 2023年第1期6卷 48-61页

作者： Mingjun Li Chao Jiang Xiaolin Song Haotian Cao State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha 410082China

Parameter effects of the potential-field-driven model predictive control(PF-MPC)method on performances of shared control systems during obstacles avoidance are *** PF-MPC controllers of autonomous driving and shared control systems are designed based on the constructed potential fields and model predictive control method,and the driver-vehicle dynamics and the driver-related costs are also considered in the design of the shared *** explore a potential approach of alleviating driver-automation conflicts of the shared control systems,different motion planning results generated by the PF-MPC controller are explored by adjusting effects of potential fields’parameters,which provides possibilities to decrease driver-automation conflicts between the planned trajectory and driver’s target ***,two case studies are designed to discuss different frameworks and parameters effects on shared control *** show that the proposed shared control frameworks considering driver-vehicle dynamics and the driver-related cost show better performances regarding driver-automation conflicts management and driving safety than the decentralized control *** the longitudinal normalized constant of potential fields parameters shows influences on the driver-automation conflicts management and driving safety performances of shared control.

关键词： PF-MPC method Potential field Parameter effect Driver-automation conflict

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Middle range wireless power transfer systems with multiple resonators

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Journal of Central South University 2015年第6期22卷 2127-2136页

作者：陈新张桂香 State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body (Hunan University) Department of Energy and Electrical Engineering Hunan University of Humanities Science and Technology

The equivalent two-port network model of a middle range wireless power transfer(WPT) system was presented based on strongly coupled multiple resonators. The key parameters of the WPT system include self-inductance, resistance, parasitic capacitance, mutual inductance and S-parameters of coils & resonators were analyzed. The impedance matching method was used to optimize load power and transmission efficiency of the multi-resonator WPT system, and the impedance matching method was realized through adjusting the distances between the coils and resonators. Experiments show that the impedance matching method can effectively improve load power and transmission efficiency for middle range wireless power transfer systems with multiple resonators, at distances up to 3 times the coil radius with efficiency more than 70% and load power also close to 3.5 W.

关键词： wireless power transfer middle range multiple resonators S-parameters two-port network impedance matching

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Electroelastic interaction between piezoelectric screw dislocation and circularly layered inclusion with imperfect interfaces

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Applied Mathematics and Mechanics(English Edition) 2013年第1期34卷 45-62页

作者：方棋洪冯慧刘又文 State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University College of Mechanical and Vehicle Engineering Hunan University

The interaction between a piezoelectric screw dislocation and an interphase layer in piezoelectric solids is theoretically investigated. Here, the dislocation located at arbitrary points inside either the matrix or the inclusion and the interfaces of the interphase layer are imperfect. By the complex variable method, the explicit solutions to the complex potentials are given, and the electroelastic fields can be derived from them. The image force acting on the dislocation can be obtained by the generalized Peach- Koehler formula. The motion of the piezoelectric screw dislocation and its equilibrium positions are discussed for variable parameters. The important results show that, if the inner interface of the interphase layer is imperfect and the magnitude of degree of the interface imperfection reaches the certain value, two equilibrium positions of the piezoelectric screw dislocation in the matrix near the interface are found for the certain material combination which has never been observed in the previous studies （without considering the interface imperfection）.

关键词： composite material dislocation piezoelectricity mechanical property

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Effect of interaction of dislocations with core-shell nanowires on critical shear stress of nanocomposites

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Journal of Central South University 2010年第3期17卷 437-442页

作者：方棋洪刘咏李慧中黄伯云 State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University State Key Laboratory of Powder Metallurgy Central South University

The contribution to the critical shear stress of nanocomposites caused by the interaction between screw dislocations and core-shell nanowires (coated nanowires) with interface stresses was derived by means of the MOTT and NABARRO's model. The influence of interface stresses on the critical shear stress was examined. The result indicates that, if the volume fraction of the core-shell nanowires keeps a constant, an optimal critical shear stress may be obtained when the radius of the nanowire with interface stresses reaches a critical value, which differs from the classical solution without considering the interface stresses under the same external conditions. In addition, the material may be strengthened by the soft nanowires when the interface stresses are considered. There also exist critical values of the elastic modulus and the thickness of surface coating to alter the strengthening effect produced by it.

关键词： nanocomposites dislocations nanowire interface stress critical shear stress

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